The present invention relates to methods and devices for applying coatings by cylindrical magnetron sputtering, in particular devices and methods where a magnetic field is created by one or more magnets.
Magnetron sputtering processes are classified as planar or cylindrical. A target provides the material to be sputtered. Several different types of cylindrical magnetron sputtering devices have been developed, as disclosed and summarized by Thornton et al., “Cylindrical Magnetron Sputtering”, 1978 Academic Press, Inc., pp. 75-113. Cylindrical magnetron sputtering devices are used to coat cylindrical workpieces, such as the inside surfaces of pipes.
The target used with planar magnetron sputtering devices can be circular, rectangular or triangular in shape. Planar magnetron sputtering targets generally suffer from non-uniform erosion, with the area of maximum erosion in the shape of a racetrack centered around the magnet position, rendering the target unusable after use, even while relatively large amounts of useful target material still remain. Basically, the target material in a cylindrical magnetron sputtering device is in the form of an elongated tube
A variety of target configurations have been described for sputtering several materials simultaneously. U.S. Pat. No. 3,477,935 describes formation of a film comprising nickel, chromium and silicon by sputtering a target body comprising a silicon body wound about with wires comprising nickel and chromium alloy; the amount of silicon in the deposited compound is described as depending on the amount and spacing of the wire on the target body, i.e. the amount of silicon surface available for sputtering. U.S. Pat. No. 4,610,774 describes a sputtering target structure suitable for use with a planar magnetron sputtering device. The sputtering target structure has a plurality of annular target members arranged concentrically with respect to a rotational symmetry axis; the target structure may have a projecting annular target member. US Patent Publication US 2004/0206620 described a rotating sputtering target segmented so as to include a plurality of different sputtering portions or segments radially dispersed around the outer periphery of the target to be sputtered to deposit a multi-layer coating; the overall shape of the sputtering target may be cylindrical.